From 83587ca0f85c912dda60f5e08a0579b9353254db Mon Sep 17 00:00:00 2001
From: Marius <maerious@gmail.com>
Date: Sat, 19 Dec 2015 00:02:11 +0100
Subject: [PATCH] Add filestore.FileLocker

---
 filestore/filelock.go      | 58 ++++++++++++++++++++++++++++++++++++++
 filestore/filelock_test.go | 35 +++++++++++++++++++++++
 2 files changed, 93 insertions(+)
 create mode 100644 filestore/filelock.go
 create mode 100644 filestore/filelock_test.go

diff --git a/filestore/filelock.go b/filestore/filelock.go
new file mode 100644
index 0000000..8184a5d
--- /dev/null
+++ b/filestore/filelock.go
@@ -0,0 +1,58 @@
+package filestore
+
+import (
+	"os"
+	"path/filepath"
+
+	"github.com/nightlyone/lockfile"
+	"github.com/tus/tusd"
+)
+
+type FileLocker struct {
+	// Relative or absolute path to store the locks in.
+	Path string
+}
+
+func (locker FileLocker) LockUpload(id string) error {
+	lock, err := locker.newLock(id)
+	if err != nil {
+		return err
+	}
+
+	err = lock.TryLock()
+	if err == lockfile.ErrBusy {
+		return tusd.ErrFileLocked
+	}
+
+	return err
+}
+
+func (locker FileLocker) UnlockUpload(id string) error {
+	lock, err := locker.newLock(id)
+	if err != nil {
+		return err
+	}
+
+	err = lock.Unlock()
+
+	// A "no such file or directory" will be returned if no lockfile was found.
+	// Since this means that the file has never been locked, we drop the error
+	// and continue as if nothing happend.
+	if os.IsNotExist(err) {
+		err = nil
+	}
+
+	return nil
+}
+
+func (locker FileLocker) newLock(id string) (lockfile.Lockfile, error) {
+	path, err := filepath.Abs(locker.Path + "/" + id + ".lock")
+	if err != nil {
+		return lockfile.Lockfile(""), err
+	}
+
+	// We use Lockfile directly instead of lockfile.New to bypass the unnecessary
+	// check whether the provided path is absolute since we just resolved it
+	// on our own.
+	return lockfile.Lockfile(path), nil
+}
diff --git a/filestore/filelock_test.go b/filestore/filelock_test.go
new file mode 100644
index 0000000..71c5c97
--- /dev/null
+++ b/filestore/filelock_test.go
@@ -0,0 +1,35 @@
+package filestore
+
+import (
+	"io/ioutil"
+	"testing"
+
+	"github.com/tus/tusd"
+	"github.com/tus/tusd/lockingstore"
+)
+
+func TestFileLocker(t *testing.T) {
+	dir, err := ioutil.TempDir("", "tusd-file-locker")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var locker lockingstore.Locker
+	locker = FileLocker{dir}
+
+	if err := locker.LockUpload("one"); err != nil {
+		t.Errorf("unexpected error when locking file: %s", err)
+	}
+
+	if err := locker.LockUpload("one"); err != tusd.ErrFileLocked {
+		t.Errorf("expected error when locking locked file: %s", err)
+	}
+
+	if err := locker.UnlockUpload("one"); err != nil {
+		t.Errorf("unexpected error when unlocking file: %s", err)
+	}
+
+	if err := locker.UnlockUpload("one"); err != nil {
+		t.Errorf("unexpected error when unlocking file again: %s", err)
+	}
+}